Tim Cook, CEO of Apple, smiles during a demonstration of the newly released Apple products following the launch event at the Steve Jobs Theater in Cupertino, California, September 12, 2018.

Apple is likely to post a huge jump in average selling price, or ASP, for the iPhone when it reports fourth-quarter earnings next week, according to top analyst Toni Sacconaghi.

The Bernstein analyst is forecasting an ASP of $800 — a record average selling price for Apple and an increase of 29 percent from Apple's fiscal fourth quarter of 2017.

That's a huge number for Apple. The days of massive unit sales growth for the iPhone appear to be over, but Apple has figured out a winning formula to squeeze more profits out of every iPhone it sells. The new family of iPhones that was introduced last month start at $750 for the iPhone XR and go all the way up to $1,449 for the fully loaded iPhone XS Max. That starting price is $100 more than the iPhone 7 cost two years ago.

iPhone XR sales won't be reflected in Apple's next earnings report since the phone goes on sale this Friday. But the XS line of phones, which starts at $1,000, went on sale at the end of last quarter. Last year's $1,000 iPhone X was available for most of the quarter as well.

In short, Apple has been able to steadily raise the price of iPhones over the last two years, which has given a boost to ASP and profits.

"Overall, we see Q4 iPhone units relatively flat on a sell-through basis and are in-line with consensus on iPhone units," Sacconaghi said in a note published Wednesday. "The more controversial question is ASPs. ... We estimate that ASPs could be significantly higher than consensus."

The average price tag on Apple's flagship phones has become an increasingly important metric in recent quarters, as global smartphone sales slow amid market saturation. The result is rapidly rising ASPs. Apple has posted double-digit year-over-year growth in ASPs for the last three fiscal quarters. The three quarters before that, ASPs were basically flat year over year.

Sacconaghi raised his price target for Apple to $225 from $200 and maintained a rating of Market Perform for the stock.